Annealed SiO2 Protective Layer on LiMn2O4 for Enhanced Li-Ion Extraction from Brine

In this study, we present a novel approach for selective Li-ion extraction from brine using an LiMn2O4 ion sieve coated with a dense silica layer, denoted as LMO@SiO2. The SiO2 layer is controllably coated onto the LMO surface, forming passivation layers and ion permeation filters. This design effectively minimizes the acidic corrosion of the LMO and enhances the Li+ adsorption capacity. Additionally, the SiO2 layer undergoes calcination at various temperatures (ranging from 300 to 700 °C) to achieve different compactness levels of the coating layer, providing further protection to the LMO crystal structures. As a result of these improvements, the optimized LMO@SiO2 adsorbent demonstrates an exceptional Li+ adsorption capacity of 18.5 mg/g for brine, and even after seven adsorption-elution cycles, it maintains a capacity of 15.3 mg/g. This outstanding performance makes our material a promising candidate for efficient Li+ extraction from brine or other low-concentration Li+ solutions in future applications.